1. Field of the Invention
The present invention relates to a wiper driving apparatus for vehicles. In particular, the present invention relates to a wiper driving apparatus for vehicles which can prevent the temporary standstill phenomenon of wiper blades by restraining the overrun phenomenon of the wiper blades during a forward rotation thereof and restraining a driving lever from rotating after an elapse of a specified time in which the driving lever stands still during a reverse rotation of the wiper blades.
2. Description of the Prior Art
FIGS. 1 and 2 show a conventional wiper driving apparatus for vehicles disclosed in Korean Un-examined Publication No. 96-37441. The conventional wiper driving apparatus includes a driving lever 20 which is fixed to and rotates in a body with a driving shaft 10 of a wiper motor, a drive-force transfer arm 40 which is connected to the driving lever 20 and reciprocates in a manner that wipers perform their own function during a forward rotation (A) of the driving lever while the wipers are parked during a reverse rotation (B) of the driving lever, and two driven arms 50, connected to a free end of the drive-force transfer arm 40, for driving two wiper arms 60 and two wiper blades 70.
According to the above apparatus, a ball bearing 30b is slidably supported on a hinge shaft of the driving lever 20 within a predetermined angle. During the forward rotation (A) of the driving lever, the ball bearing 30b rotates in a direction nearing the rotating shaft of the driving lever 20 as it traces a relatively small circular arc, and thus the wiper blade 70 rotates by a predetermined rotating angle including a start position (S) and a return position (R) so that the wipers perform their own function. During the reverse rotation (B) of the driving lever, the ball bearing 30b slidably moves in a direction getting away from the rotating shaft of the driving lever 20 as it traces a relatively large circular arc, and thus the wiper blade 70 moves to a parking position (P) which is deeper than the start position (S).
Also, according to the above apparatus, the driving lever 20 is structured to be folded in one direction. During the forward rotation (A) thereof, the hinge point of the outer end of the driving lever 20 rotates to trace the relatively small circular arc in a state that the driving lever 20 is folded to a predetermined angle, and thus the wiper blade 70 is driven to move in forward and reverse directions. During the reverse rotation (B) of the driving lever 20, the hinge point of the outer end of the driving lever 20 rotates to trace the relatively large circular arc as the driving lever is unfolded, and thus the wiper blade 70 moves to the parking position (P) which is deeper than the start position (S).
However, the conventional wiper driving apparatus has the drawbacks that during the forward rotation (A) of the driving lever 20, the overrun phenomenon of the wiper blade 70 happens as the outmost hinge point of the driving lever 20 or the position of the ball bearing 30b is changed due to the inertial force of rotation of the wiper. Also, at the time point when the angle of the reverse rotation (B) of the driving lever 20 reaches about 45.degree. as the driving lever 20 rotates reversely from the return position (R) to trace the relatively large circular arc, the driving lever 20 becomes unfolded, or the ball bearing 30b, which is slidably supported on the plate type driving lever 20 within the predetermined angle, rapidly slides in the direction getting away from the rotating shaft of the wiper driving motor after its temporary standstill state, so that the wiper blade 70 rotates after the specified waiting time with noises, deteriorating the operational reliability of the wiper.
Specifically, in the parking operation of the wiper blades 70 according to the conventional wiper driving apparatus, the ball bearing 30b, which is eccentrically arranged on the hinge shaft of the driving lever 20, rotates and moves in the upward direction getting away from the driving shaft of the wiper driving motor as it traces the large circular arc during the reverse rotation of the driving lever 20. At this time, the inertial force of rotation of the wiper affects the drive-force transfer arm 40, and the position of the ball bearing 30b connected to the drive-force transfer arm 40 is changed during its rotation, resulting in that the wiper blade 70 rotates over the predetermined rotating angle, and this causes the overrun phenomenon of the wiper blade 70, which is the rapid rotation of the wiper blade 70 after the specified waiting time, to happen.
The overrun phenomenon may cause the driver to misrecognize it as malfunction of the wiper driving apparatus. The overrun phenomenon also degrades the visual field of the driver especially in case of rain, resulting in an uncomfortable driving state.